408 



BELL SYSTEM TECHNICAL JOURNAL 



Fig, 



2000 



1600 



1200 



800 



400 



-800 



-t200 



-1600 



-2000 



2500 



3100 



2600 2700 2800 2900 3000 

 FREQUENCY IN CYCLES PER SECOND 



5 — Acoustic impedance of closed cylindrical tube, 2.4 inches long and 0.7 inch 

 in diameter, showing agreement between measured and calculated values. 



50 



U 40 



^ 20 



200 



500 1000 2000 



FREQUENCY IN CYCLES PER SECOND 



Fig. 6 — Acoustic impedance of .38 inch conical horn, having end diameters of 0.7 inch 



and 28 inches. 



